Fuel control apparatus



ct. 4, E949., L. A. WILLIAMS, JR 2,483,747

FUEL CONTROL APPARATUS Filed May-2. 1945 2 Sheets-Sheet 2 Patented Oct.4, 1949 FUEL CONTROL APPARATUS Lynn A. Williams, Jr., Northfield, Ill.,assignor to Stewart-Warner Corporation, Chicago, lll., a corporation ofVirginia Application May 2, 1945, serial No. 591,543

1 Claim.

My invention relates generally to fuel control apparatus, particularlyapparatus for controlling the flow of liquid fuel to =a vehicle heater.

In liquid -fuel burning heaters of .the sealed combustion type, as usedfor example for heating the passenger compartments of automobiles, thefuel is supplied from the engine operated fuel pump of the automobile,and the pressure at which the fuel is supplied to the heater maytherefore vary throughout a substantial range. depending upon the speedof operation of the engine. In heaters of this type, it is commonpractice to utilize an electric igniter of the hot wire type. A shortinterval of time is required to heat it to a temperature at which itwill ignite the fuel, and, if the fuel is supplied .to the'heater duringthis time interval, some of the fuel may pass through the heater withoutbeing burned, -or it may collect in various parts of the heater.Furthermore, the presence of .the fuel in the heater while the igniteris being heated to its ignition temperature, slows down the heating ofthe igniter because some of the heat generated thereby is lost invaporizing the fuel prior to the time that the igniter is hot enough toignite the vapor.

It is therefore one of the -obiects of the invention to provide animproved fue1 control valve for heaters, in Iwhich ythe opening of thefuel supply valve is delayed until the igniter has been heated to atemperature at which .it can ignite the fuel.

A further object of the invention is to provide an improved electricallycontrolled fuel valve.

A further object is to provide `a fuel line valve which operates toregulate the pressure at which the fuel is supplied, and also iselectrically operated to permit and stop the flow of fuel.

Other objects will appear from Ithe following description, referencebeing had to the :accompanying drawings, in which:

Fig. 1 is a schematic wiring diagram of the control circuits anddiagrammatically illustrates the control elements, parts of the heaterbeing shown in phantom;

Fig. 2 is a central vertical sectional view of the improved controlvalve, taken on the line 2-2 of Fig. 3; and Y Fig. 3 is a sectional viewtaken on the line 3--3 of Fig. 2.

Referring to Fig. 1, a heater I is illustrated in phantom as comprisinga casing l2 in which is located a heat exchanger i4 and a combustionchamber I6, from which lthe products of combustion flow through the heatexchanger and are discharged through Ian exhaust conduit i8. Fuel issupplied to the combustion chamber i6 through va pipe 2B from a suitablesource, such as the fuel pump of an automobile. The flow of fuel throughthe pipe 2t is controlled by a fuel valve 22, while air for combustionis supplied .to the combustion chamber through ya conduit 24.

An electrical igniter 226 of the hot wire type is suitably located toignite the fuel mixture in the combustion chamber, and has one of its.terminals grounded. The other terminal is adapted to be connected to asource of electrical energy such as the automobile battery '28, througha thermostatic igniter deenergizing switch 30, a thermostatic overheatswitch 32, and Va manually operable heater control main switch 34.

Located in the passenger compartment of the automobile, or in any otherspace to be heated by the heater, is a control switch S comprising aninsulating support 38 for la pair of thermostatic bimetal switch arms 48and 4|. The setting of the switch Iarm 4B may be varied by means of anadjusting thumb screw 42.

The switch arm 4! has a heating coil 44 wound about it, but electricallyinsulated therefrom. A heating coil 46 is similarly wound about one legof a U-shaped bimetal thermostatic actuator 48 forming part of the fuelvalve 22. -One terminal of the heating coil 46 is grounded, while theother terminal is connected'to the switch arm 4D, the circuit to thebattery 28 being completed through the heating coil 44, overheat switch32, and main switch 34.

When the main switch is closed, assuming the heater to be cold and theoverheat switch 32 and igniter deenergizing switch closed, and assumingfurther that the switch arms 40 `and 4l are in the positions shown andthe switch 36 thus closed, closure of the main switch 34 will result insupplying current to the igniter 26 and also to the two heating coils 44and 46.

When the switch arm 4| is heated, it fleXes downwardly Itending to moveaway from the switch arm 40. The switch larm 4Q moves downwardly whencold s-o that the switch will remain closed for a longer interval whenthe passenger compartment is cold than when it is warm. As long as theswitch 3E remains closed, current is also supplied to the heating coil46 which, as 4presently will appear, operates in a manner to open thefuel valve when its heating coil 46 iS energized. The heating coils 44`and 45 are of relatively high resistance so that the bimetals aroundwhich they are wound will heat up rather 3 slowly, thus introducing atime delay in the operation `of )the fuel valve.

The fuel valve 22 is preferably of the construction illustrated in Figs.2 and 3, and comprises a body 50 having the fuel supply pipe 2lconnected thereto to supply fuel through an inlet port 52. A Valve seatmember 54 is threaded in the body 50 and is provided with a valve seat56 and a port 58. Within the valve seat member 54 there is a cylindricalbore providing a guide for a valve stem 60, which is of noncircularcross section to provide `a passageway 62 for the ow of fuel. A valvedisc 64 is secured to the valve stem 60 by a shouldered pin 6B pressedinto the stem. The stem 66 is recessed to receive a helical coil spring68 which rests upon an apertured centering seat 1D and normally holdsthe valve disc 64 in engagement with its seat 56.

A flexible diaphragm 12 has its edge clamped between the body 22 and aplate 'i4 by a plurality of cap screws 16. The diaphragm l2 has acentral opening which is closed by a member 78, the latter beingsuitably clamped to the diaphragm in a fuel tight manner. The member I8has a bore for the reception of a compression coil spring 86, the upperturn of which is of reduced diameter and has a ballbearing 52 silversoldered or brazed thereto. The U-shaped bimetal 48 is symmetrical andhas one end of one leg 8| thereof fastened to the plate '14 by l.

screws l5. The other leg B3- of this U-shaped bimetal which has theelectrical heater winding 44 thereon, has its end located directly abovethe ball B2 so as normally to be in contact therewith, The leg Si flexesin response to ambient temperature and thus acts as an ambienttemperature compensator for the leg 83. The U- shaped bimetal isprotected by a thin sheet metal cover 84 and the space enclosed by thiscover has free access to the atmosphere through a hole 86 formed in theplate i4. The ow through the pipe will be restricted by a small orice ina well known manner.

In operation, the main switch 34 is closed by the operator of thevehicle, thus supplying current through the normally closed overheatswitch 38, the heater winding 44, switch 36, and heater winding 46. Inaddition, current will be supplied to the igniter 26 through the igniterdenergizing switch 30.

As the leg 83 of the Umshaped bimetal 46 is heated, its free end pressesdownwardly upon the diaphragm through the spring 86, and after it hasbeen heated for alength of time suicient for the igniter 26 to haveattained ignition temperature, will exert a sufficient force in adownward direction upon the pin 66 to move the the'valve disc 64 fromits seat 56. Fuel may therefore flow past the valve into the chamberbeneath the diaphragm '12, exerting pressure thereon opposing thatapplied by the leg 83. At the same time, the bimetal switch arm 4i willbe heated and commence flexing downwardly. Such downward flexure will,under the usual operating conditions, ce accompanied by a correspondingilexure of the bimetal arm 46 so that the switch 36 will remain closedfor substantial time interval.

As soon as the fuel commences flowing to the heater past the valve 6d,it will be ignited, `by the igniter and Ventilating air flowing throughthe casing l2 will commence delivering heat to the space to be heated.As the heater approaches its normal operating temperature, the igniterdeenergizing switch 36 will open, As the space in which the controlswitch 36 is located becomes heated, the/bimetal switch arm 40 will tendto flex upwardly and when a temperature determined by the adjustment'ofthe thumb nut 42 is attained, the switch 36 will open, thereby cuttingoff the supply of current to the two heater windings 44 and 46.

Due to the residual heat in the leg 83, it will be some time before thepressure which this leg applies to the pin 65 will be relievedsufficiently to permit the spring 68 to close the valve 64. By the timethat the force applied by the leg 83 is no longer sufficient to hold thevalve 66 open, the bimetal switch arm 4I will Kalso have cooled andflexed upwardly so as again to close the switch 36, thereby reenergizingthe heater windings 44 and 46, whereupon the cycle of operation of theswitch 36 and leg 33 will be repeated.

As the pressure of the fuel within the chamber beneath the diaphragmbuilds up, the pressure which is exerted on the diaphragm 'l2 by thefuel will tend to cause the valve 64 to move toward closed position,such movement being permitted but resisted by the spring and theresiliency of the U-shaped bimetal 48.

Due to the time constant of the cycle imposed by the time required toheat and cool the bimetal switch arm 4l, fuel will usually becontinuously supplied to the heater, but the average rate at which itows will depend upon the relative length of time that the switch 36 isclosed and opened. This is `caused by the fact that when the switch isclosed for a longer interval, the leg 8l will be heated to a highertemperature and therefore hold the valve 64 open for a longer period oftime and permit the fuel in the chamber below the diaphragm 12 to attaina higher pressure, and thus an increased flow rate. The length of theportion of the cycle during which the switch 36 is closed is, of course,determined by the temperature of the air in the space being heated, asit affects the switch arm 46, for the reason that as the temperaturedrops, the switch arm 40 will flex downwardly and the switch arm 4! willhave to be heated to a higher temperature before it is effective to openthe switch 36, and correspondingly. this switch will be open for ashorter length of time because the switch arm M will take a shorter timeto cool to a temperature at which it fleXes upwardly suiiciently againto make contact with the switch arm 40.

As is customary in heaters of this type, the igniter deenergizing switch3@ recloses upon sufficient cooling of the heater, due to failure ofcombustion, while the overheat switch 32 will be opened whenever thenormal operating temperature of the heater is materially exceeded.

It will thus be clear from the foregoing that the control systemoperates Vin an eiilcient and reliable manner to control the pressure atwhich fuel is supplied to the heater, and that this control means is notonly responsive to the temperature of the space being heated, but alsohas provisions to prevent opening of the fuel supply valve until acertain time suiicient for the igniter to attain ignition temperaturehas elapsed.

While I have shown and described a preferred embodiment of my invention,it will be apparent that numerous variations and modifications thereofmay be made without departing from the underlying principles of theinvention. I therefore desire, by the following claim, to include withinthe scope of the invention all such variations and modifications bywhich substantially the results of my invention may be obtained throughthe use of substantially the same or equivalent means.

I claim:

In an electrically controlled valve apparatus, the combination of avalve body having a valve seat therein and having a chamber, a valvecooperable with said seat, a diaphragm forming one wall of the chamber,resilient means urging said valve against said seat, a thermostaticbimetal element, a resilient operating connection between said bimetalelement and said valve, electrical means to heat said bimetal elementthereby to cause the latter to apply a force through said resilientoperating connection in a direction to open said valve, and meansresponsive to ambient temperature to energize said electrical heatingmeans intermittently for intervals of increasing length as the ambienttemperature decreases.

LYNN A. WILLIAMS, JR.

6 REFERENCES CITED The following references are of record in the le ofthis patent:

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